Semiconductor wafers are typically fabricated with multiple copies of a desired integrated circuit design that will later be separated and made into individual chips. Wafers are commonly constructed in layers, where a portion of a circuit is created on a layer and conductive vias are created to electrically connect the circuit to other layers. After each layer of the circuit is etched on the wafer, an oxide layer is put down allowing the vias to pass through but covering the rest of the previous circuit layer. In one instance, each layer of the circuit can create or add unevenness to the wafer that is typically smoothed before generating the next circuit layer.
Chemical mechanical planarization (CMP) techniques can be used to planarize the raw wafer and each layer of material added thereafter. Available CMP systems are commonly called wafer polishers. Often such a wafer polisher will include a rotating wafer carrier head. The wafer carrier head may bring the wafer into contact with a polishing pad. In a rotary CMP system, the polishing pad may be circularly rotated in the plane of the wafer surface to be planarized. A polishing fluid, such as a chemical polishing agent or slurry containing micro abrasives may be applied to the polishing surface to polish the wafer. The wafer is pressed against the rotating polishing pad and is rotated to polish and planarize the wafer. Another CMP technique uses a linear polisher. Instead of a rotating pad, a moving belt is used to linearly move the polishing pad across the rotating wafer surface.
As the wafer is polished, the polishing pad also becomes smoother or planarized. Additionally, residue from the slurry and/or reaction byproducts may influence the performance of the pad conditioner. The consistency in polishing multiple wafers is an important aspect of planarization of wafers. To maintain the surface of the polishing pad at a consistent level of abrasiveness, a pad conditioner may be used. The pad conditioner may similarly be pressed into the moving polishing pad. The surface of the pad conditioner that is pressed into the polishing pad may include an abrasive substance, such as diamond grit, to scratch or roughen the surface of the polishing pad.
During the process of conditioning the polishing pad, undesirable residue may be generated that can vary the consistency of wafer polishing. In addition, localized heating may occur in the area where the pad conditioner is conditioning the polishing pad. The localized heating may cause undesirable melting of the polishing pad and/or localized drying of the polishing pad that may affect the consistency of wafer polishing. Accordingly, there is a need for systems and methods for controlling the residue and localized heating associated with conditioning a polishing pad.